Industrial machines, such as dozers, motor graders, wheel loaders, and other types of heavy equipment are used to perform a variety of tasks. The completion of some of these tasks requires operation of the machines on or near steep inclines that have the potential to cause engine and machine damage. For example, when operated on a steep incline, a machine may be instructed to enter a gear that is inappropriate for the particular incline. As a result, the machine may be able to move too quickly, or the engine may be driven to rotate at a speed above a damage threshold. When the machine is being controlled by an on-board human operator, these engine and machine conditions can be anticipated by the operator and manually avoided.
In some situations, such as during remote or autonomous control of a machine, it may not be possible for a human operator to sufficiently anticipate the effects of worksite conditions on operation of the engine or machine. For example, the operator may be unable to hear the engine, sense the pitch of the machine, or feel accelerations indicative of machine operation relative to engine, transmission, and/or worksite conditions. In addition, a remote operator may be more prone to directing the machine to travel into areas of the worksite, such as voids in a coal pile or across steep inclines, that should not be traversed above a certain speed or transmission gear.
Moreover, the remote operator may be unable to predict or avoid engine over-speed conditions and detrimental gear changes. For example, a remote operator could instruct a machine operating at the top end of its second gear to switch into its first gear, thereby over-speeding, or “over-revving” the engine. The remote operator could also cause gear changes that jeopardize the entire machine. For example, if the remote operator instructs a machine operating in its first gear down a steep incline, to switch into its second gear, the machine may accelerate too quickly. Accordingly, there is a need for an automated machine retarding system and method.
An automated machine retarder system is described in U.S. Pat. No. 6,299,263 (the '263 patent) issued to Uematsu, et al. on Oct. 9, 2001. The automated retarder system of the '263 patent controls the speed of a mine vehicle as it descends a slope. The retarder system includes a controller in communication with a plurality of detectors, such as a vehicle speed detector; an actuator, such as a braking mechanism; an operator display unit; and a manual input switch. The controller operates the braking mechanism based on parameters received from the detectors, such as the inclination of the vehicle, the oil temperature, the current gear, the operator inputs, and the vehicle speed, so as to prevent brake overheating and to maintain the vehicle at a constant hill descent speed.
Although the system of the '263 patent may help minimize the likelihood of brake overheating and related vehicle freewheeling on a steep slope, it may not be able to completely stop a vehicle. Therefore, it may be ineffective in preventing vehicle freewheeling occurring as a result of being inadvertently left on a slope in a neutral condition. Likewise, the system of the '263 patent may be unable to prevent engine overspeed conditions and detrimental gear changes occurring in a vehicle that is being remotely-operated on a slope. That is, even though the system of the '263 patent may take into consideration various parameters for controlling vehicle descent speed, the system only uses the parameters so as to maintain a descent speed slow enough to prevent the brakes from overheating. As a result, the system of the '263 patent may be ineffective for preventing other causes of damage to the engine and machine.
The disclosed system is directed to overcoming one or more of the problems set forth above.